Gas Well Testing Handbook
Offering a thorough understanding of gas well test analysis basics, this book focuses on practical field application, where over 100 field examples are presented to illustrate basic methods for analysis.
TABLE OF CONTENTS Gas Well Testing Handbook
6.10: Other Methods for Analyzing Pressure Buildup Test Data
6.10 Other Methods for Analyzing Pressure Buildup Test Data
Several other methods for analyzing pressure buildup data are available and are reviewed in this section.
MDH Method
This method3 also uses the MDH plot, but the method is limited to estimating average reservoir pressure in a closed circular or square drainage region and to wells operating at pseudo-steady-state before the buildup test. The following equations and Figure 6 16 are used. Equation 6 9 can be written for large producing times, that is, for t P ? ?t, to become
Figure 6 16: Comparison of times required to reach the end of Horner and MDH straight line (after Cobb and Smith).7
Hence a plot of ?( p ws) versus ? t on semilogarithmic coordinates should give a straight line of slope m, from which kh may be calculated. The apparent skin factor s ? may be obtained from Eq. 6 11. The average reservoir pseudopressure ?( p R) is obtained from Figure 5 12 for various shapes. The value of ? t De is calculated at any chosen shut-in time ?t from
where 
for noncircular geometry.
The corresponding value of ?p D is obtained from Figure B 5. The average reservoir pressure is then calculated from
where m = slope of the MDH semilog straight line and ?( p ws) = value of the pseudopressure corresponding to the chosen shut-in time ?t from the straight...
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